Onomoto Koji, Sakai Monami, Watanabe Miyu, Fukao Akira, Sakamura Yurika, Miyao Mai, Tomohiro Takumi, Yamashita Akio, Fujiwara Toshinobu, Takahashi Tomoko, Ui-Tei Kumiko, Yoneyama Mitsutoshi
Division of Molecular Immunology, Medical Mycology Research Center, Chiba University, Chiba, 260-8673, Japan.
Laboratory of Biochemistry, Department of Pharmacy, Kindai University, Higashi-Osaka, 577-8502, Japan.
Sci Rep. 2025 Jul 1;15(1):20678. doi: 10.1038/s41598-025-07121-3.
Stress granules (SGs) are dense aggregates of RNA and proteins that form in response to various cellular stresses. Virus-induced SGs, known as antiviral SGs (avSGs), play a crucial role in regulating retinoic acid-inducible gene I-like receptors (RLRs)-mediated antiviral innate immunity. However, the regulation of avSG formation remains not fully understood. In this study, we demonstrate that TAR-RNA binding protein (TRBP), an RNA silencing regulator, negatively regulates type I interferon (IFN) expression by inhibiting avSG formation in response to RNA virus infection. Overexpression of TRBP inhibits both IFN-β promoter activity and avSG formation following viral infection or the viral RNA mimic, polyinosinic-polycytidylic acid transfection. TRBP knockout cells exhibit enhanced phosphorylation and activation of IFN regulatory factor-3 (IRF-3) and increased IFN-β mRNA expression compared to wild-type cells. Additionally, depletion of G3BP1 and G3BP2, which are essential for SG formation, abolishes the inhibitory effect of TRBP on IRF-3 phosphorylation. Mechanistically, TRBP physically interacts with double-stranded RNA (dsRNA)-dependent protein kinase R (PKR), a key kinase involved in avSG formation, via its dsRNA-binding domains, and inhibits PKR activation. In summary, our findings reveal a novel function for TRBP as a negative regulator of RLR-mediated signaling through PKR-dependent inhibition of avSG formation.
应激颗粒（SGs）是RNA和蛋白质的致密聚集体，在细胞受到各种应激时形成。病毒诱导的SGs，即抗病毒SGs（avSGs），在调节视黄酸诱导基因I样受体（RLRs）介导的抗病毒天然免疫中起关键作用。然而，avSG形成的调控机制仍未完全阐明。在本研究中，我们证明RNA沉默调节因子TAR-RNA结合蛋白（TRBP）通过抑制RNA病毒感染时avSG的形成，负向调节I型干扰素（IFN）的表达。TRBP过表达抑制病毒感染或病毒RNA模拟物聚肌苷酸-聚胞苷酸转染后IFN-β启动子活性和avSG形成。与野生型细胞相比，TRBP基因敲除细胞中IFN调节因子-3（IRF-3）的磷酸化和激活增强，IFN-β mRNA表达增加。此外，SG形成所必需的G3BP1和G3BP2的缺失消除了TRBP对IRF-3磷酸化的抑制作用。机制上，TRBP通过其双链RNA结合结构域与双链RNA（dsRNA）依赖性蛋白激酶R（PKR）发生物理相互作用，PKR是参与avSG形成的关键激酶，并抑制PKR激活。总之,我们的研究结果揭示了TRBP作为一种负调节因子具有新功能，即通过PKR依赖的avSG形成抑制作用来负调节RLR介导的信号传导。
