Sigma 28-dependent small RNAs regulate timing of flagella biosynthesis

Synthesis of flagella is very energy intensive and, while extensive transcriptional regulation has been described, little is known about the post-transcriptional regulation. Small RNAs (sRNAs) are widespread posttranscriptional regulators; most base pairing with mRNAs to affect their stability and/or translation. Here we describe four UTR-derived sRNAs (UhpU, MotR, FliX and FlgO) whose expression is controlled by the flagella sigma factor, sigma 28 in Escherichia coli. UhpU, MotR and FliX have distinct impacts on flagellin levels, flagella number and swimming, with MotR accelerating flagella synthesis and FliX decelerating flagella synthesis. Interestingly, MotR and FliX are noncanonical in that they base pair within the coding sequences of target genes. We characterize their respective positive and negative effects on genes encoding ribosomal proteins. Overall design: Total RNA sequencing of E. coli strains carrying a control vector or overexpressing MotR* or FliX-S

鞭毛合成过程能耗极高，尽管其转录调控机制已有广泛研究，但目前对其转录后调控的认知仍十分有限。小型RNA（small RNAs, sRNAs）是一类分布广泛的转录后调控因子，多数可通过与信使RNA（mRNA）进行碱基互补配对，影响靶mRNA的稳定性及/或翻译过程。本研究报道了4种源自非翻译区（untranslated regions, UTRs）的小型RNA（UhpU、MotR、FliX与FlgO），它们在大肠杆菌（Escherichia coli）中的表达受鞭毛特异性σ因子σ28的调控。UhpU、MotR与FliX对鞭毛蛋白水平、鞭毛数量及游泳运动能力具有显著差异化的调控效果：其中MotR可加速鞭毛合成，而FliX则会延缓鞭毛合成过程。值得注意的是，MotR与FliX属于非经典小型RNA，它们能够在靶基因的编码序列内与靶RNA发生碱基配对。本研究解析了这三种sRNA分别对核糖体蛋白编码基因的正向与负向调控效应。实验设计概况：对携带空载体对照、过表达MotR*或FliX-S的大肠杆菌菌株开展总RNA测序。