沈锡辉、张磊等《Nature Communications》2023年
论文题目：c-di-GMP inhibitsthe DNA bindingactivity ofH-NS in Salmonella
论文作者：Shuyu Li, Qinmeng Liu, Chongyi Duan, Jialin Li, Hengxi Sun, Lei Xu, Qiao Yang, Yao Wang,Xihui Shen*,Lei Zhang*
论文摘要：Cyclic di-GMP (c-di-GMP) is a second messenger that transduces extracellular stimuli into cellular responses and regulates various biological processes in bacteria. H-NS is a global regulatory protein that represses expression of many genes, but how H-NS activity is modulated by environmental signals remains largely unclear. Here, we show that high intracellular c-di-GMP levels, induced by environmental cues, relieve H-NS-mediated transcriptional silencing in Salmonella enterica serovar Typhimurium. We find that c-di-GMP binds to the H-NS protein to inhibit its binding to DNA, thus derepressing genes silenced by H-NS. However, c-di-GMP is unable to displace H-NS from DNA. In addition, a K107A mutation in H-NS abolishes response to c-di-GMP but leaves its DNA binding activity unaffected in vivo. Our results thus suggest a mechanism by which H-NS acts as an environment-sensing regulator in Gram-negative bacteria.
c-di-GMP是细菌中广泛存在的一类核苷类第二信使，能够响应外界环境和宿主信号调控细菌的众多生理和病理过程。组蛋白样类核结构蛋白H-NS是广泛分布于革兰氏阴性细菌中的一类全局性转录调控因子，参与调控数百个毒力、代谢、环境应激反应等相关基因的表达。本研究首先发现胆汁酸盐通过c-di-GMP信号途径激活沙门氏菌VI型分泌系统(T6SS)的活性，并以此为切入点，筛选鉴定出抑制T6SS基因表达的H-NS为c-di-GMP的作用靶点。进一步研究表明，c-di-GMP与H-NS结合后，封闭了H-NS的部分DNA结合位点，导致H-NS无法结合DNA，从而解除H-NS对基因表达的抑制作用。转录组测序结果显示，胞内c-di-GMP水平上升后还能减轻H-NS对SPI-2、SPI-3、SPI-5等毒力基因表达的抑制。本研究揭示了H-NS响应外界信号调控基因表达的一种新模式，丰富了对c-di-GMP信号受体感应及调控机制的认知，同时为抗细菌感染药物研发提供了新靶点。