Dai Jingli, Chen Zijing, Hou Jinfeng, Wang Yudong, Guo Miao, Cao Jiajia, Wang Liangyan, Xu Hong, Tian Bing, Zhao Ye
Institute of Biophysics, College of Life Sciences, Zhejiang University, Hangzhou, China.
MOE Key Laboratory of Biosystems Homeostasis and Protection, Zhejiang University, Hangzhou, China.
Front Genet. 2021 Feb 19;12:632423. doi: 10.3389/fgene.2021.632423. eCollection 2021.
shows marked resistance to various types of DNA-damaging agents, including mitomycin C (MMC). A type II toxin-antitoxin (TA) system that responds to DNA damage stress was identified in , comprising the toxin MazF-dr and the antitoxin MazE-dr. The cleavage specificity of MazF-dr, an endoribonuclease, was previously characterized. Here, we further investigated the regulatory role of the MazEF system in the response to DNA damage stress in . The crystal structure of MazF (MazF-dr) was determined at a resolution of 1.3 Å and is the first structure of the toxin of the TA system of . MazF-dr forms a dimer mediated by the presence of interlocked loops. Transcriptional analysis revealed 650 downregulated genes in the wild-type (WT) strain, but not in the mutant strain, which are potentially regulated by MazEF-dr in response to MMC treatment. Some of these genes are involved in membrane trafficking and metal ion transportation. Subsequently, compared with the WT strain, the mutant strain exhibited much lower MMC-induced intracellular iron concentrations, reactive oxygen species (ROS), and protein carbonylation levels. These results provide evidence that MazEF-mediated cell death in might be caused by an increase in ROS accumulation upon DNA damage stress.
对包括丝裂霉素C（MMC）在内的各种类型的DNA损伤剂表现出显著抗性。在[具体物种]中鉴定出一种对DNA损伤应激有反应的II型毒素-抗毒素（TA）系统，它由毒素MazF-dr和抗毒素MazE-dr组成。先前已对核酸内切酶MazF-dr的切割特异性进行了表征。在此，我们进一步研究了MazEF系统在[具体物种]对DNA损伤应激反应中的调节作用。以1.3 Å的分辨率测定了MazF（MazF-dr）的晶体结构，这是[具体物种]TA系统毒素的首个结构。MazF-dr通过互锁环的存在形成二聚体。转录分析显示野生型（WT）菌株中有650个基因下调，但在[具体突变体]突变菌株中未下调，这些基因可能受MazEF-dr调控以响应MMC处理。其中一些基因参与膜运输和金属离子转运。随后，与WT菌株相比，[具体突变体]突变菌株表现出MMC诱导的细胞内铁浓度、活性氧（ROS）和蛋白质羰基化水平低得多。这些结果提供了证据，表明[具体物种]中MazEF介导的细胞死亡可能是由DNA损伤应激时ROS积累增加引起的。
