Tuti Nikhil, Rathnam Sharan Shanmuga Vuppaladadium, Jangra Jitender, Rath Subha Narayan, Meur Gargi, Anindya Roy
Department of Biotechnology, Indian Institute of Technology Hyderabad (IITH), Sangareddy, Telangana, India.
Regenerative Medicine and Stem Cell Laboratory (RMS), Department of Biomedical Engineering, Indian Institute of Technology Hyderabad (IITH), Sangareddy, Telangana, India.
Immunol Cell Biol. 2025 Sep;103(8):784-793. doi: 10.1111/imcb.70047. Epub 2025 Jul 21.
The immune system uses a variety of DNA sensors, including endo-lysosomal Toll-like receptors 9 (TLR9) and cytosolic DNA sensor cyclic GMP-AMP (cGAMP) synthase (cGAS). These sensors activate immune responses by inducing the production of a variety of cytokines, including type I interferons (IFN). Activation of cGAS requires DNA-cGAS interaction. Accumulation of cGAMP activates the stimulator of interferon genes (STING), ultimately leading to pathogen clearance by type I IFN production. To prevent the sensing of endogenous nuclear DNA, cGAS is usually localized in the cytoplasm. In this work, we studied the interaction and activation of cGAS by DNA containing non-CpG methyl adducts N3-methyl-C (3mC) and 7-methyl-G (7mG). We report that while DNA with 3mC and 7mG interacts with cGAS, it fails to stimulate its activity in vitro. To gain mechanistic insight, we used synthetic oligonucleotides containing 3mC and 7mG for cGAS activation. We observed that the presence of these adducts was inhibitory to cGAS-catalyzed cGAMP production and type I IFN response in human monocyte cell line THP1. Thus, our study reveals that the specific DNA base methylation adducts 3mC and 7mG contribute to the regulation of cGAS activation and provide a potential strategy for delivering DNA without activating the cGAS pathway.
免疫系统利用多种DNA传感器，包括内溶酶体Toll样受体9（TLR9）和胞质DNA传感器环磷酸鸟苷-腺苷酸（cGAMP）合酶（cGAS）。这些传感器通过诱导包括I型干扰素（IFN）在内的多种细胞因子的产生来激活免疫反应。cGAS的激活需要DNA与cGAS相互作用。cGAMP的积累激活干扰素基因刺激因子（STING），最终通过产生I型干扰素来清除病原体。为了防止对内源性核DNA的感应，cGAS通常定位于细胞质中。在这项工作中，我们研究了含有非CpG甲基加合物N3-甲基胞嘧啶（3mC）和7-甲基鸟嘌呤（7mG）的DNA与cGAS的相互作用及激活情况。我们报告称，虽然含有3mC和7mG的DNA与cGAS相互作用，但它在体外无法刺激其活性。为了深入了解其机制，我们使用含有3mC和7mG的合成寡核苷酸来激活cGAS。我们观察到这些加合物的存在对人单核细胞系THP1中cGAS催化的cGAMP产生和I型干扰素反应具有抑制作用。因此，我们的研究表明，特定的DNA碱基甲基化加合物3mC和7mG有助于调节cGAS的激活，并为在不激活cGAS途径的情况下传递DNA提供了一种潜在策略。
