Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India.
Division of Bacteriology, National Institute for Cholera and Enteric Diseases, Kolkata 700010, India.
Nucleic Acids Res. 2018 Apr 20;46(7):3429-3445. doi: 10.1093/nar/gky126.
Many bacterial genomes exclusively display an N4-methyl cytosine base (m4C), whose physiological significance is not yet clear. Helicobacter pylori is a carcinogenic bacterium and the leading cause of gastric cancer in humans. Helicobacter pylori strain 26695 harbors a single m4C cytosine methyltransferase, M2.HpyAII which recognizes 5' TCTTC 3' sequence and methylates the first cytosine residue. To understand the role of m4C modification, M2.hpyAII deletion strain was constructed. Deletion strain displayed lower adherence to host AGS cells and reduced potential to induce inflammation and apoptosis. M2.hpyAII gene deletion strain exhibited reduced capacity for natural transformation, which was rescued in the complemented strain carrying an active copy of M2.hpyAII gene in the genome. Genome-wide gene expression and proteomic analysis were carried out to discern the possible reasons behind the altered phenotype of the M2.hpyAII gene deletion strain. Upon the loss of m4C modification a total of 102 genes belonging to virulence, ribosome assembly and cellular components were differentially expressed. The present study adds a functional role for the presence of m4C modification in H. pylori and provides the first evidence that m4C signal acts as a global epigenetic regulator in H. pylori.
许多细菌基因组专门显示 N4-甲基胞嘧啶碱基（m4C），其生理意义尚不清楚。幽门螺杆菌是一种致癌细菌，是人类胃癌的主要病因。幽门螺杆菌菌株 26695 仅含有一个 m4C 胞嘧啶甲基转移酶 M2.HpyAII，它识别 5' TCTTC 3' 序列并甲基化第一个胞嘧啶残基。为了了解 m4C 修饰的作用，构建了 M2.hpyAII 缺失菌株。缺失菌株对宿主 AGS 细胞的黏附能力降低，诱导炎症和细胞凋亡的能力降低。M2.hpyAII 基因缺失菌株的自然转化能力降低，在基因组中携带活性 M2.hpyAII 基因的互补菌株中得到挽救。进行了全基因组基因表达和蛋白质组学分析，以发现 M2.hpyAII 基因缺失菌株表型改变的可能原因。在失去 m4C 修饰后，共有 102 个属于毒力、核糖体组装和细胞成分的基因表达差异。本研究为 H. pylori 中 m4C 修饰的存在增加了一个功能作用，并提供了第一个证据表明 m4C 信号作为 H. pylori 中的全局表观遗传调节剂发挥作用。
