Wei Yanxia, Li Yang, Yang Fan, Wu Qiong, Liu Dianbin, Li Xiangyang, Hua Hui, Liu Xiaomei, Wang Yugang, Zheng Kuiyang, Tang Renxian
Department of Pathogenic Biology and Immunology, Jiangsu Key Laboratory of Immunity and Metabolism, Xuzhou Medical University, Xuzhou, China.
Jiangsu Vocational College of Nursing, Huaian, China.
Appl Environ Microbiol. 2017 Apr 17;83(9). doi: 10.1128/AEM.03232-16. Print 2017 May 1.
strain JDM301, a widely used commercial strain in China, encodes at least two MazEF-like modules and one RelBE-like toxin-antitoxin (TA) system in its chromosome, designated MazEF, MazEF, and RelBE, respectively. Bacterial TA systems play an important role in several stress responses, but the relationship between these TA systems is largely unknown. In this study, the interactions between MazF and MazE or RelB were assessed in strain JDM301. MazF caused the degradation of mRNA, and its toxicity was inhibited by forming a protein complex with its cognate antitoxin, MazE Notably, MazF toxicity was also partially neutralized when jointly expressed with noncognate antitoxin MazE or RelB Our results show that the two noncognate antitoxins also inhibited mRNA degradation caused by MazF toxin. Furthermore, the physical interplay between MazF and its noncognate antitoxins was confirmed by immunoprecipitation. These results suggest that MazF can arrest cell growth and that MazF toxicity can be neutralized by its cognate and noncognate antitoxins. These results imply that JDM301 uses a sophisticated toxin-antitoxin interaction network to alter its physiology when coping with environmental stress. Although toxin-antitoxin (TA) systems play an important role in several stress responses, the regulatory mechanisms of multiple TA system homologs in the bacterial genome remain largely unclear. In this study, the relationships between MazEF and the other two TA systems of strain JDM301 were explored, and the interactions between MazF and MazE or RelB were characterized. In addition, the mRNA degradation activity of MazF was demonstrated. In particular, the interaction of the toxin with noncognate antitoxins was shown, even between different TA families (MazF toxin and RelB antitoxin) in JDM301. This work provides insight into the regulatory mechanisms of TA systems implicated in the stress responses of bifidobacteria.
菌株JDM301是中国广泛使用的商业菌株，其染色体中编码至少两个MazEF样模块和一个RelBE样毒素-抗毒素（TA）系统，分别命名为MazEF、MazEF和RelBE。细菌TA系统在多种应激反应中发挥重要作用，但这些TA系统之间的关系在很大程度上尚不清楚。在本研究中，评估了菌株JDM301中MazF与MazE或RelB之间的相互作用。MazF导致mRNA降解，其毒性通过与其同源抗毒素MazE形成蛋白质复合物而受到抑制。值得注意的是，当与非同源抗毒素MazE或RelB共同表达时，MazF的毒性也会部分被中和。我们的结果表明，这两种非同源抗毒素也能抑制MazF毒素引起的mRNA降解。此外，通过免疫沉淀证实了MazF与其非同源抗毒素之间的物理相互作用。这些结果表明，MazF可阻止细胞生长，且MazF的毒性可被其同源和非同源抗毒素中和。这些结果意味着，JDM301在应对环境压力时利用复杂的毒素-抗毒素相互作用网络来改变其生理状态。尽管毒素-抗毒素（TA）系统在多种应激反应中发挥重要作用，但细菌基因组中多个TA系统同源物的调控机制在很大程度上仍不清楚。在本研究中，探索了菌株JDM301中MazEF与其他两个TA系统之间的关系，并对MazF与MazE或RelB之间的相互作用进行了表征。此外，还证明了MazF的mRNA降解活性。特别是，展示了毒素与非同源抗毒素之间的相互作用，甚至在JDM301中不同的TA家族（MazF毒素和RelB抗毒素）之间也是如此。这项工作为双歧杆菌应激反应中涉及的TA系统调控机制提供了见解。
