G3BP1 Knockout Cell Line (HEK293)

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.

The detection of intracellular nucleic acids is a fundamental mechanism of host defense against infections. The dysregulated nucleic acid sensing, however, is a major cause for a number of autoimmune diseases. In this study, we report that GTPase-activating protein SH3 domain-binding protein 1 (G3BP1) is critical for both intracellular DNA- and RNA-induced immune responses. We found that in both human and mouse cells, the deletion of G3BP1 led to the dampened cGAS activation by DNA and the insufficient binding of RNA by RIG-I. We further found that resveratrol (RSVL), a natural compound found in grape skin, suppressed both intracellular DNA- and RNA-induced type I IFN production through inhibiting G3BP1. Importantly, using experimental mouse models for Aicardi-Goutières syndrome, an autoimmune disorder found in humans, we demonstrated that RSVL effectively alleviated intracellular nucleic acid-stimulated autoimmune responses. Thus, our study demonstrated a broader role of G3BP1 in sensing different kinds of intracellular nucleic acids and presented RSVL as a potential treatment for autoimmune conditions caused by dysregulated nucleic acid sensing.