Blanchard Laurence, Guérin Philippe, Roche David, Cruveiller Stéphane, Pignol David, Vallenet David, Armengaud Jean, de Groot Arjan
Lab Bioenerget Cellulaire, CEA, DRF, BIAM, Saint-Paul-lez-Durance, France.
CNRS, UMR 7265 Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, France.
Microbiologyopen. 2017 Aug;6(4). doi: 10.1002/mbo3.477. Epub 2017 Apr 11.
The extreme radiation resistance of Deinococcus bacteria requires the radiation-stimulated cleavage of protein DdrO by a specific metalloprotease called IrrE. DdrO is the repressor of a predicted radiation/desiccation response (RDR) regulon, composed of radiation-induced genes having a conserved DNA motif (RDRM) in their promoter regions. Here, we showed that addition of zinc ions to purified apo-IrrE, and short exposure of Deinococcus cells to zinc ions, resulted in cleavage of DdrO in vitro and in vivo, respectively. Binding of IrrE to RDRM-containing DNA or interaction of IrrE with DNA-bound DdrO was not observed. The data are in line with IrrE being a zinc peptidase, and indicate that increased zinc availability, caused by oxidative stress, triggers the in vivo cleavage of DdrO unbound to DNA. Transcriptomics and proteomics of Deinococcus deserti confirmed the IrrE-dependent regulation of predicted RDR regulon genes and also revealed additional members of this regulon. Comparative analysis showed that the RDR regulon is largely well conserved in Deinococcus species, but also showed diversity in the regulon composition. Notably, several RDR genes with an important role in radiation resistance in Deinococcus radiodurans, for example pprA, are not conserved in some other radiation-resistant Deinococcus species.
耐辐射球菌的极端抗辐射能力需要一种名为IrrE的特定金属蛋白酶对蛋白质DdrO进行辐射刺激切割。DdrO是一个预测的辐射/干燥反应（RDR）调控子的阻遏物，该调控子由在其启动子区域具有保守DNA基序（RDRM）的辐射诱导基因组成。在这里，我们表明，向纯化的脱辅基IrrE中添加锌离子，以及将耐辐射球菌细胞短暂暴露于锌离子，分别导致体外和体内的DdrO切割。未观察到IrrE与含RDRM的DNA结合或IrrE与DNA结合的DdrO相互作用。这些数据与IrrE是一种锌肽酶一致，并表明由氧化应激引起的锌可用性增加会触发未与DNA结合的DdrO在体内的切割。沙漠耐辐射球菌的转录组学和蛋白质组学证实了IrrE对预测的RDR调控子基因的依赖性调控，并还揭示了该调控子的其他成员。比较分析表明，RDR调控子在耐辐射球菌物种中在很大程度上是保守的，但也显示出调控子组成的多样性。值得注意的是，一些在耐辐射奇异球菌的抗辐射中起重要作用的RDR基因，例如pprA，在其他一些抗辐射耐辐射球菌物种中并不保守。
