Agroécologie, AgroSup Dijon, INRA, Université de Bourgogne Franche-Comté , Dijon , France.
Bacterial Stress Response Group, National University of Ireland , Galway , Ireland.
RNA Biol. 2019 Oct;16(10):1424-1437. doi: 10.1080/15476286.2019.1632776. Epub 2019 Jun 26.
The facultative intracellular pathogen can persist and grow in a diverse range of environmental conditions, both outside and within its mammalian host. The alternative sigma factor Sigma B (σ) plays an important role in this adaptability and is critical for the transition into the host. While some of the functions of the σ regulon in facilitating this transition are understood the role of σ-dependent small regulatory RNAs (sRNAs) remain poorly characterized. In this study, we focused on elucidating the function of Rli47, a σ-dependent sRNA that is highly induced in the intestine and in macrophages. Using a combination of and approaches, a binding interaction was predicted with the Shine-Dalgarno region of the mRNA, which encodes threonine deaminase, an enzyme required for branched-chain amino acid biosynthesis. Both transcript levels and threonine deaminase activity were increased in a deletion mutant lacking the gene. The Δ mutant displayed a shorter growth lag in isoleucine-depleted growth media relative to the wild-type, and a similar phenotype was also observed in a mutant lacking σ. The impact of the Δ on the global transcription profile of the cell was investigated using RNA-seq, and a significant role for Rli47 in modulating amino acid metabolism was uncovered. Taken together, the data point to a model where Rli47 is responsible for specifically repressing isoleucine biosynthesis as a way to restrict growth under harsh conditions, potentially contributing to the survival of in niches both outside and within the mammalian host.
兼性细胞内病原体可以在各种环境条件下生存和生长，包括其哺乳动物宿主的内外环境。替代 sigma 因子 Sigma B（σ）在这种适应性中起着重要作用，对于进入宿主至关重要。虽然 σ 调控子在促进这种转变中的一些功能已经得到理解，但 σ 依赖的小调节 RNA（sRNA）的作用仍知之甚少。在这项研究中，我们专注于阐明 Rli47 的功能，Rli47 是一种在肠道和巨噬细胞中高度诱导的 σ 依赖性 sRNA。我们使用 和 方法的组合，预测了与编码苏氨酸脱氨酶的 mRNA 的 Shine-Dalgarno 区域的结合相互作用，苏氨酸脱氨酶是支链氨基酸生物合成所必需的酶。在缺乏 基因的缺失突变体中， 转录本水平和苏氨酸脱氨酶活性均增加。与野生型相比，Δ 突变体在缺乏异亮氨酸的生长培养基中的生长滞后更短，而在缺乏 σ 的突变体中也观察到类似的表型。使用 RNA-seq 研究了 Δ 对细胞全局转录谱的影响，并发现 Rli47 在调节氨基酸代谢方面具有重要作用。综上所述，数据表明，Rli47 负责特异性抑制异亮氨酸生物合成，以此在恶劣条件下限制生长，这可能有助于 在哺乳动物宿主内外的小生境中生存。
