ARNA Laboratory, Inserm U1212, CNRS UMR 5320, Université de Bordeaux, France.
Nucleic Acids Res. 2019 Jun 20;47(11):5906-5921. doi: 10.1093/nar/gkz258.
In most bacteria, ribosomal RNA is transcribed as a single polycistronic precursor that is first processed by RNase III. This double-stranded specific RNase cleaves two large stems flanking the 23S and 16S rRNA mature sequences, liberating three 16S, 23S and 5S rRNA precursors, which are further processed by other ribonucleases. Here, we investigate the rRNA maturation pathway of the human gastric pathogen Helicobacter pylori. This bacterium has an unusual arrangement of its rRNA genes, the 16S rRNA gene being separated from a 23S-5S rRNA cluster. We show that RNase III also initiates processing in this organism, by cleaving two typical stem structures encompassing 16S and 23S rRNAs and an atypical stem-loop located upstream of the 5S rRNA. Deletion of RNase III leads to the accumulation of a large 23S-5S precursor that is found in polysomes, suggesting that it can function in translation. Finally, we characterize a cis-encoded antisense RNA overlapping the leader of the 23S-5S rRNA precursor. We present evidence that this antisense RNA interacts with this precursor, forming an intermolecular complex that is cleaved by RNase III. This pairing induces additional specific cleavages of the rRNA precursor coupled with a rapid degradation of the antisense RNA.
在大多数细菌中，核糖体 RNA 作为单个多顺反子前体转录，首先由 RNase III 进行加工。这种双链特异性 RNase 切割侧翼 23S 和 16S rRNA 成熟序列的两个大茎，释放出三个 16S、23S 和 5S rRNA 前体，它们进一步被其他核糖核酸酶加工。在这里，我们研究了人类胃病原体幽门螺杆菌的 rRNA 成熟途径。这种细菌的 rRNA 基因排列异常，16S rRNA 基因与 23S-5S rRNA 簇分离。我们表明，RNase III 也通过切割包含 16S 和 23S rRNAs 的两个典型茎结构和位于 5S rRNA 上游的非典型茎环，在该生物体中起始加工。RNase III 的缺失导致大量 23S-5S 前体的积累，该前体存在于多核糖体中，表明它可以在翻译中发挥作用。最后，我们表征了一个顺式编码的反义 RNA，该 RNA 与 23S-5S rRNA 前体的前导序列重叠。我们提供的证据表明，这种反义 RNA 与该前体相互作用，形成一个由 RNase III 切割的分子间复合物。这种配对诱导 rRNA 前体的额外特异性切割，并伴随着反义 RNA 的快速降解。
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