MazEF and MqsRA are toxin-antitoxin systems, where the toxins MazF and MqsR sequence-specifically cleave single-stranded RNA, thereby shutting down protein synthesis and cell growth. However, it has been proposed that MazF functions in a highly specific pathway, where it truncates the 5' ends of a set of E. coli transcripts (the MazF regulon), which are then translated under stress conditions by specialized ribosomes. We mapped the cleavage sites of MazF and MqsR throughout the E. coli transcriptome. Our results show that both toxins cleave mRNA independently of the recognition site position and MazF freely cleaves transcripts of the proposed MazF regulon within coding sequences. Proteome analysis indicated that MazF expression leads to overall inhibition of protein synthesis and the putative MazF regulon proteins are not selectively synthesized in response to the toxin. Our results support a simpler role for endoribonuclease TA systems as indifferent destroyers of unstructured RNA.

MazEF和MqsRA是毒素抗毒素系统，其中毒素MazF和MqsR序列特异性切割单链RNA，从而关闭蛋白质合成和细胞生长。然而，已经提出，MazF在高度特异性的途径中起作用，在其中它截短一组大肠杆菌转录物（MazF regulon）的5'末端，然后在应激条件下由专门的核糖体翻译。我们绘制了整个大肠杆菌中MazF和MqsR的切割位点转录组。我们的结果表明，这两种毒素均会独立于识别位点位置而切割mRNA，而MazF会自由地在编码序列内切割拟议的MazF regulon的转录本。蛋白质组学分析表明，MazF表达导致蛋白质合成的全面抑制，推定的MazF调节子蛋白并未响应毒素而选择性合成。我们的结果支持内切核糖核酸酶TA系统作为非结构化RNA的无害破坏者的简单作用。