Center for Infectious Disease Research, Beijing Frontier Research Center for Biological Structure and Beijing Advanced Innovation Center for Structural Biology, Department of Basic Medical Sciences, School of Medicine, Tsinghua University, Beijing, China.
Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan, China.
EMBO Rep. 2023 Feb 6;24(2):e51800. doi: 10.15252/embr.202051800. Epub 2022 Nov 16.
Cyclic GMP-AMP synthase (cGAS) is a double-stranded DNA (dsDNA) sensor that functions in the innate immune system. Upon binding dsDNA, cGAS and dsDNA form phase-separated condensates in which cGAS catalyzes the synthesis of 2'3'-cyclic GMP-AMP that subsequently triggers a STING-dependent, type I interferon (IFN-I) response. Here, we show that cytoplasmic RNAs regulate cGAS activity. We discover that RNAs do not activate cGAS but rather promote phase separation of cGAS in vitro. In cells, cGAS colocalizes with RNA and forms complexes with RNA. In the presence of cytoplasmic dsDNA, RNAs colocalize with phase-separated condensates of cGAS and dsDNA. Further in vitro assays showed that RNAs promote the formation of cGAS-containing phase separations and enhance cGAS activity when the dsDNA concentration is low. Cotransfection of RNA with a small amount of dsDNA into THP1 cells significantly enhances the production of the downstream signaling molecule interferon beta (IFNB). This enhancement can be blocked by a cGAS-specific inhibitor. Thus, cytoplasmic RNAs could regulate cGAS activity by modulating the formation of cGAS-containing condensates.
环鸟苷酸-腺苷酸合酶 (cGAS) 是一种双链 DNA (dsDNA) 传感器，在先天免疫系统中发挥作用。cGAS 与 dsDNA 结合后，在其中形成相分离凝聚物，cGAS 在此凝聚物中催化 2'3'-环鸟苷酸-腺苷酸的合成，随后触发 STING 依赖性 I 型干扰素 (IFN-I) 反应。在这里，我们表明细胞质 RNA 调节 cGAS 活性。我们发现 RNA 本身不会激活 cGAS，但会促进 cGAS 在体外相分离。在细胞中，cGAS 与 RNA 共定位并与 RNA 形成复合物。在细胞质 dsDNA 存在的情况下，RNA 与 cGAS 和 dsDNA 的相分离凝聚物共定位。进一步的体外实验表明，当 dsDNA 浓度较低时，RNA 促进包含 cGAS 的相分离的形成并增强 cGAS 活性。将少量 dsDNA 与 RNA 共转染到 THP1 细胞中，可显著增强下游信号分子干扰素β (IFNB) 的产生。这种增强可以被 cGAS 特异性抑制剂阻断。因此，细胞质 RNA 可以通过调节包含 cGAS 的凝聚物的形成来调节 cGAS 活性。
