Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Mol Cell. 2018 Jun 7;70(5):868-880.e10. doi: 10.1016/j.molcel.2018.04.026. Epub 2018 May 31.
Toxin-antitoxin systems are widely distributed genetic modules that regulate growth and persistence in bacteria. Many systems, including E. coli MazEF, include toxins that are endoribonucleases, but the full set of targets for these toxins remains poorly defined. Previous studies on a limited set of transcripts suggested that MazF creates a pool of leaderless mRNAs that are preferentially translated by specialized ribosomes created through MazF cleavage of mature 16S rRNA. Here, using paired-end RNA sequencing (RNA-seq) and ribosome profiling, we provide a comprehensive, global analysis of MazF cleavage specificity and its targets. We find that MazF cleaves most transcripts at multiple sites within their coding regions, with very few full-length, leaderless mRNAs created. Additionally, our results demonstrate that MazF does not create a large pool of specialized ribosomes but instead rapidly disrupts ribosome biogenesis by targeting both ribosomal protein transcripts and rRNA precursors, helping to inhibit cell growth.
毒素-抗毒素系统广泛分布于调节细菌生长和存活的遗传模块中。许多系统，包括大肠杆菌 MazEF，都包含内核糖核酸酶毒素，但这些毒素的全部靶标仍未得到很好的定义。之前对一组有限的转录本的研究表明，MazF 产生了一个无 5' 帽 mRNA 池，这些 mRNA 被通过成熟 16S rRNA 切割产生的特殊核糖体优先翻译。在这里，我们使用配对末端 RNA 测序（RNA-seq）和核糖体图谱分析，对 MazF 切割特异性及其靶标进行了全面的、全局的分析。我们发现，MazF 在其编码区的多个位点切割大多数转录本，很少产生全长、无 5' 帽的 mRNA。此外，我们的结果表明，MazF 并没有产生大量的特殊核糖体，而是通过靶向核糖体蛋白转录本和 rRNA 前体，快速破坏核糖体生物发生，从而有助于抑制细胞生长。
