Specificity and Evolutionary Conservation of the Escherichia coil RNA Pyrophosphohydrolase RppH
Specificity and Evolutionary Conservation of the Escherichia coil RNA Pyrophosphohydrolase RppH
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DOI：
10.1074/jbc.m114.634659
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发表时间：
2015-04-10
影响因子：
4.8
通讯作者：
Belasco, Joel G.
中科院分区：
文献类型：
--
作者：
Foley, Patricia L.;Hsieh, Ping-kun;Belasco, Joel G.
细菌 RNA 降解通常始于 RNA 焦磷酸水解酶 RppH 将 5' 末端三磷酸转化为单磷酸，这一事件会触发快速核糖核酸水解攻击。 RppH 除了作为 5' 端依赖性 mRNA 衰变的主要调节因子外，对于病原菌侵入宿主细胞的能力也很重要，但人们对其如何选择靶标却知之甚少。在这里，我们表明，称为 RppH (EcRppH) 的埃希氏菌在 RNA 5' 末端需要至少两个不配对的核苷酸，并且更喜欢三个或更多这样的核苷酸。它可以容忍前三个位置的任何核苷酸，但对 5' 末端的 A 和第二个位置的 G 或 A 有一定的偏好。突变分析已鉴定出对底物识别或催化至关重要的 EcRppH 残基。 EcRppH 的混杂性使其与具有严格 RNA 序列要求的枯草芽孢杆菌对应物区分开来。 EcRppH 直系同源物可能具有宽松的序列特异性，广泛存在于除 Deltaproteobacteria 之外的所有变形菌纲以及开花植物中。相比之下，可识别的枯草芽孢杆菌 RppH 直系同源物的系统发育范围似乎仅限于芽孢杆菌目。这些发现有助于解释 RppH 对细菌 mRNA 降解的选择性影响，并表明 RppH 依赖性降解在进化过程中显着多样化。
Bacterial RNA degradation often begins with conversion of the 5'-terminal triphosphate to a monophosphate by the RNA pyrophosphohydrolase RppH, an event that triggers rapid ribonucleolytic attack. Besides its role as the master regulator of 5'-end-dependent mRNA decay, RppH is important for the ability of pathogenic bacteria to invade host cells, yet little is known about how it chooses its targets. Here, we show that Escherichia call RppH (EcRppH) requires at least two unpaired nucleotides at the RNA 5' end and prefers three or more such nucleotides, It can tolerate any nucleotide at the first three positions but has a modest preference for A at the 5' terminus and either a G or A at the second position. Mutational analysis has identified EcRppH residues crucial for substrate recognition or catalysis. The promiscuity of EcRppH differentiates it from its Bacillus subtilis counterpart, which has a strict RNA sequence requirement. EcRppH orthologs likely to share its relaxed sequence specificity are widespread in all classes of Proteobacteria, except Deltaproteobacteria, and in flowering plants. By contrast, the phylogenetic range of recognizable B. subtilis RppH orthologs appears to be restricted to the order Bacillales. These findings help to explain the selective influence of RppH on bacterial mRNA decay and show that RppH-dependent degradation has diversified significantly during the course of evolution.