Department of Mycobacteriology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
Department of Mycobacteriology, Leprosy Research Center, National Institute of Infectious Diseases, Tokyo, Japan.
Tuberculosis (Edinb). 2020 Mar;121:101890. doi: 10.1016/j.tube.2019.101890. Epub 2019 Nov 18.
CpG motifs in DNA sequences are recognized by Toll-like receptor 9 and activate immune cells. Bacterial genomic DNA (gDNA) has modified cytosine bases (5-methylcytosine [5 mC]) and modified adenine bases (6-methyladenine [6 mA]). 5 mC inhibits immune activation by CpG DNA; however, it is unclear whether 6 mA inhibits immune activation by CpG DNA. Mycobacterium bovis BCG (BCG) has three adenine methyltransferases (MTases) that act on specific target sequences. In this study, we examined whether the 6 mA at the target sites of adenine MTases affected the immunostimulatory activity of CpG DNA. Our results showed that only 6 mA located at the target sequence of mamA, an adenine MTase from BCG, enhanced interleukin (IL)-12p40 production from murine bone marrow-derived macrophages (BMDMs) stimulated with CpG DNA. Enhancement of IL-12p40 production in BMDMs was also observed when BMDMs were stimulated with CpG DNA ligated to oligodeoxynucleotides (ODNs) harboring 6 mA. Accordingly, we then evaluated whether gDNA from adenine MTase-deficient BCG was less efficient with regard to stimulation of BMDMs. Indeed, gDNA from a mamA-deficient BCG had less ability to activate BMDMs than that from wild-type BCG. We concluded from these results that adenine methylation on ODNs and bacterial gDNA may enhance immune activity induced by CpG DNA.
CpG 基序在 DNA 序列中被 Toll 样受体 9 识别，并激活免疫细胞。细菌基因组 DNA（gDNA）具有修饰的胞嘧啶碱基（5-甲基胞嘧啶[5mC]）和修饰的腺嘌呤碱基（6-甲基腺嘌呤[6mA]）。5mC 抑制 CpG DNA 的免疫激活；然而，6mA 是否抑制 CpG DNA 的免疫激活尚不清楚。牛分枝杆菌卡介苗（BCG）有三种腺嘌呤甲基转移酶（MTases），作用于特定的靶序列。在这项研究中，我们研究了腺嘌呤 MTase 靶位点的 6mA 是否影响 CpG DNA 的免疫刺激活性。结果表明，只有 BCG 中一种腺嘌呤 MTase mamA 的靶序列中的 6mA 增强了 CpG DNA 刺激的小鼠骨髓来源巨噬细胞（BMDM）中白细胞介素（IL）-12p40 的产生。当用含有 6mA 的寡脱氧核苷酸（ODN）连接的 CpG DNA 刺激 BMDM 时，也观察到 IL-12p40 产生的增强。因此，我们随后评估了腺嘌呤 MTase 缺陷 BCG 的 gDNA 在刺激 BMDM 方面的效率是否较低。事实上，mamA 缺陷 BCG 的 gDNA 激活 BMDM 的能力比野生型 BCG 的 gDNA 差。我们从这些结果中得出结论，ODN 和细菌 gDNA 上的腺嘌呤甲基化可能增强 CpG DNA 诱导的免疫活性。
