Institut National de la Santé et de la Recherche Médicale, Bacterial Regulatory RNAs and Medicine UMR_S 1230, Rennes, France.
Department of Chemistry and Biochemistry, Bern University, Bern, Switzerland.
Nat Microbiol. 2021 Feb;6(2):209-220. doi: 10.1038/s41564-020-00819-2. Epub 2021 Jan 4.
Persister cells are a subpopulation of transiently antibiotic-tolerant bacteria associated with chronic infection and antibiotic treatment failure. Toxin-antitoxin systems have been linked to persister cell formation but the molecular mechanisms leading to bacterial persistence are mostly unknown. Here, we show that SprF1, a type I antitoxin, associates with translating ribosomes from the major human pathogen Staphylococcus aureus to reduce the pathogen's overall protein synthesis during growth. Under hyperosmotic stress, SprF1 levels increase due to enhanced stability, accumulate on polysomes and attenuate protein synthesis. Using an internal 6-nucleotide sequence on its 5'-end, SprF1 binds ribosomes and interferes with initiator transfer RNA binding, thus reducing translation initiation. An excess of messenger RNA displaces the ribosome-bound antitoxin, freeing the ribosomes for new translation cycles; however, this RNA antitoxin can also displace ribosome-bound mRNA. This translation attenuation mechanism, mediated by an RNA antitoxin, promotes antibiotic persister cell formation. The untranslated SprF1 is a dual-function RNA antitoxin that represses toxin expression by its 3'-end and fine-tunes overall bacterial translation via its 5'-end. These findings demonstrate a general function for a bacterial RNA antitoxin beyond protection from toxicity. They also highlight an RNA-guided molecular process that influences antibiotic persister cell formation.
持留细胞是与慢性感染和抗生素治疗失败相关的短暂抗生素耐受细菌的亚群。毒素-抗毒素系统与持留细胞的形成有关，但导致细菌持续存在的分子机制在很大程度上尚不清楚。在这里，我们表明，SprF1 是一种 I 型抗毒素，与来自主要人类病原体金黄色葡萄球菌的翻译核糖体结合，以减少病原体在生长过程中的整体蛋白合成。在高渗应激下，由于稳定性增强，SprF1 水平增加，在多核糖体上积累并减弱蛋白质合成。SprF1 利用其 5' 端的内部 6 个核苷酸序列与核糖体结合，并干扰起始转移 RNA 的结合，从而减少翻译起始。过量的信使 RNA 取代核糖体结合的抗毒素，使核糖体能够进行新的翻译循环；然而，这种 RNA 抗毒素也可以取代核糖体结合的 mRNA。这种由 RNA 抗毒素介导的翻译衰减机制促进了抗生素持留细胞的形成。未翻译的 SprF1 是一种具有双重功能的 RNA 抗毒素，通过其 3' 端抑制毒素表达，并通过其 5' 端微调细菌的整体翻译。这些发现证明了细菌 RNA 抗毒素除了具有保护免受毒性之外的一般功能。它们还突出了一个影响抗生素持留细胞形成的 RNA 指导的分子过程。
