N6-methylated adenine on the target sites of mamA from Mycobacterium bovis BCG enhances macrophage activation by CpG DNA in mice

• Published in: Tuberculosis (Edinburgh, Scotland) Vol. 121; p. 101890
• Main Authors: Tsukamoto, Yumiko, Tamura, Toshiki, Maeda, Yumi, Miyake, Kensuke, Ato, Manabu
• Format: Journal Article
• Language: English
• Published: Scotland Elsevier Ltd 01.03.2020; Elsevier Science Ltd
• Subjects: Adenine; Bacillus Calmette-Guerin vaccine; BCG; Bone marrow; Cell activation; CpG islands; Cytosine; Deoxyribonucleic acid; DNA; DNA methylation; Gene sequencing; Genomics; Immune response; Immune system; Immunostimulation; Interleukin 12; Interleukins; Macrophages; Mycobacterium bovis; Nucleotide sequence; Oligonucleotides; Proteins; Toll-like receptors; PS; 6 mA; M-CSF; BCG; BM; hygr; Dam; PD; MTases; TLR9; BMDMs; MTB; 5 mC; ODNs; gDNA
• ISSN: 1472-9792; 1873-281X
• DOI: 10.1016/j.tube.2019.101890

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. [Display omitted]