Zhu Ling, Inoue Koichi, Yoshizumi Satoshi, Kobayashi Hiroshi, Zhang Yonglong, Ouyang Ming, Kato Fuminori, Sugai Motoyuki, Inouye Masayori
Department of Biochemistry, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
J Bacteriol. 2009 May;191(10):3248-55. doi: 10.1128/JB.01815-08. Epub 2009 Feb 27.
Escherichia coli mRNA interferases, such as MazF and ChpBK, are sequence-specific endoribonucleases encoded by toxin-antitoxin (TA) systems present in its genome. A MazF homologue in Staphylococcus aureus (MazF(Sa)) has been shown to inhibit cell growth when induced in E. coli. Here, we determined the cleavage site for MazF(Sa) with the use of phage MS2 RNA as a substrate and CspA, an RNA chaperone, which prevents the formation of secondary structures in the RNA substrate. MazF(Sa) specifically cleaves the RNA at a pentad sequence, U downward arrow ACAU. Bioinformatics analysis revealed that this pentad sequence is significantly abundant in several genes, including the sraP gene in the S. aureus N315 strain. This gene encodes a serine-rich protein, which is known to play an important role in adhesion of the pathogen to human tissues and thus in endovascular infection. We demonstrated that the sraP mRNA became extremely unstable in comparison with the ompA mRNA only when MazF(Sa) was induced in E. coli. Further bioinformatics analysis indicated that the pentad sequence is also significantly abundant in the mRNAs for all the pathogenic factors in S. aureus. This observation suggests a possible regulatory relationship between the MazEF(Sa) TA module and the pathogenicity in S. aureus.
大肠杆菌mRNA干扰酶，如MazF和ChpBK，是由其基因组中存在的毒素-抗毒素（TA）系统编码的序列特异性核糖核酸内切酶。金黄色葡萄球菌中的一种MazF同源物（MazF(Sa)）已被证明在大肠杆菌中诱导表达时会抑制细胞生长。在这里，我们以噬菌体MS2 RNA为底物，利用RNA伴侣蛋白CspA（其可防止RNA底物中二级结构的形成）来确定MazF(Sa)的切割位点。MazF(Sa)特异性地在一个五联体序列U↓ACAU处切割RNA。生物信息学分析表明，该五联体序列在包括金黄色葡萄球菌N315菌株中的sraP基因在内的几个基因中显著富集。该基因编码一种富含丝氨酸的蛋白质，已知其在病原体与人组织的黏附中起重要作用，进而在血管内感染中起作用。我们证明，仅当在大肠杆菌中诱导表达MazF(Sa)时，与ompA mRNA相比，sraP mRNA变得极其不稳定。进一步的生物信息学分析表明，该五联体序列在金黄色葡萄球菌所有致病因子的mRNA中也显著富集。这一观察结果提示了MazEF(Sa) TA模块与金黄色葡萄球菌致病性之间可能存在调控关系。
