Data Sheet 1_A novel small RNA regulates Locus of Enterocyte Effacement and site-specific colonization of enterohemorrhagic Escherichia coli O157:H7 in gut.pdf

Enterohemorrhagic Escherichia coli (EHEC) is a contagious foodborne pathogen that specifically colonizes the human large intestine, which is regulated by different environmental stimuli within the gut. Transcriptional regulation of EHEC virulence and infection has been extensively studied, while the posttranscriptional regulation of these processes by small RNAs (sRNAs) remains not fully understood. Here we present a virulence-regulating pathway in EHEC O157:H7, in which the sRNA EvrS binds to and destabilizes the mRNA of Z2269, a novel transcriptional regulator. In turn, Z2269 indirectly activates the expression of LEE (locus of enterocyte effacement) pathogenicity island through the master regulator Ler. Importantly, the expression of EvrS is modulated by environmental oxygen levels. EvrS also exhibits lower expression in the colon compared to the ileum, influencing the site-specific colonization of EHEC O157:H7 in mice. These results indicate that the oxygen status within the intestine may regulate the expression of EvrS, thereby modulating virulence factors of EHEC and contributing to successful infection in vivo. This study has broader implications for understanding sRNA functions in spatiotemporal virulence control of EHEC and may provide novel strategies to prevent EHEC infections.

肠出血性大肠杆菌（Enterohemorrhagic Escherichia coli, EHEC）是一类传染性食源性致病菌，可特异性定殖于人类大肠，其定殖过程受肠道内多种环境刺激信号的调控。目前针对肠出血性大肠杆菌毒力与感染过程的转录调控机制已开展广泛研究，但由小RNA（small RNAs, sRNAs）介导的上述过程的转录后调控机制仍未完全明晰。本研究报道了肠出血性大肠杆菌O157:H7中的一条毒力调控通路：小RNA EvrS可结合并降解新型转录调控因子Z2269的mRNA；随后Z2269通过主调控因子Ler，间接激活肠细胞脱落位点（locus of enterocyte effacement, LEE）致病岛的表达。尤为关键的是，EvrS的表达受环境氧浓度的调控；且相较于回肠，EvrS在结肠中的表达水平更低，这会影响肠出血性大肠杆菌O157:H7在小鼠体内的位点特异性定殖。上述研究结果表明，肠道内的氧合状态可通过调控EvrS的表达，进而调节肠出血性大肠杆菌的毒力因子表达，最终助力其在宿主体内成功建立感染。本研究对于阐明小RNA在肠出血性大肠杆菌时空特异性毒力调控中的功能具有更广泛的科学意义，同时可为预防肠出血性大肠杆菌感染提供全新的干预策略。