Li Lamei, Yan Huan, Feng Lipeng, Li Yunlong, Lu Pei, Hu Yangbo, Chen Shiyun
Center for Emerging Infectious Diseases, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China.
PLoS One. 2014 Mar 21;9(3):e92243. doi: 10.1371/journal.pone.0092243. eCollection 2014.
Pathogenic Yersinia species employ the Ysc-Yop type III secretion system (T3SS) encoded by a highly conserved pYV virulence plasmid to export the virulence effectors into host cells. The Ysc-Yop T3SS is tightly regulated by multiple contributing proteins that function at different levels. However, systematic transcriptional regulation analysis of Ysc-Yop T3SS is lacking and the detailed mechanism under this regulation process is still elusive. Aimed at systematically characterizing transcriptional regulations of all T3SS genes in Y. pseudotuberculosis, we amplified 97 non-coding fragments from the pYV plasmid and analyzed transcriptional responses of the T3SS genes under different growth conditions. Transcriptions of T3SS genes were induced at 37°C and genes encoding T3SS effectors were highly induced by further depletion of Ca2+. The temperature induced gene transcription process is mediated by modules encoded on the chromosome, while the Ca2+ depletion-induced process is controlled by the positive regulatory protein LcrF as well as the negative regulatory protein LcrQ. In this process, LcrQ shares the same targets with LcrF and the effect of LcrQ is dependent on the presence of LcrF. Furthermore, over-expression of LcrF showed the same phenotype as that of the lcrQ mutant strain and intracellular amount balance of LcrQ and LcrF is important in T3SS regulation. When the expression level of LcrF exceeds LcrQ, expression of the Ysc-Yop T3SS genes is activated and vice versa. Together, these data support a model in which LcrQ blocks the activation role of LcrF in regulating the transcription of T3SS genes in Yersinia.
致病性耶尔森菌属利用由高度保守的pYV毒力质粒编码的Ysc-Yop III型分泌系统(T3SS)将毒力效应蛋白输出到宿主细胞中。Ysc-Yop T3SS受到多种在不同水平发挥作用的蛋白质的严格调控。然而,缺乏对Ysc-Yop T3SS的系统转录调控分析,并且该调控过程的详细机制仍不清楚。为了系统地表征假结核耶尔森菌中所有T3SS基因的转录调控,我们从pYV质粒中扩增了97个非编码片段,并分析了T3SS基因在不同生长条件下的转录反应。T3SS基因的转录在37°C时被诱导,并且编码T3SS效应蛋白的基因在进一步耗尽Ca2+时被高度诱导。温度诱导的基因转录过程由染色体上编码的模块介导,而Ca2+耗尽诱导的过程由正调控蛋白LcrF以及负调控蛋白LcrQ控制。在这个过程中,LcrQ与LcrF具有相同的靶标,并且LcrQ的作用依赖于LcrF的存在。此外,LcrF的过表达表现出与lcrQ突变株相同的表型,并且LcrQ和LcrF的细胞内量平衡在T3SS调控中很重要。当LcrF的表达水平超过LcrQ时,Ysc-Yop T3SS基因的表达被激活,反之亦然。总之,这些数据支持了一个模型,即LcrQ在耶尔森菌中阻断LcrF在调节T3SS基因转录中的激活作用。