IRF3 activates RB to authorize cGAS-STING-induced senescence and mitigate liver fibrosis

Cytosolic dsDNA surveillance by cGAS-STING signaling triggers autophagy, biased mRNA translation, cellular senescence, and interferon-mediated immune responses. However, detailed mechanisms and physiological relevance of STING-induced senescence are not fully understood. Here, we unexpectedly found that IRF3, activated during innate DNA sensing, forms substantial endogenous complexes in the nucleus with retinoblastoma (RB), a well-known tumor suppressor and key cell cycle regulator. The IRF3-RB interaction attenuates CDK4/6-mediated hyperphosphorylation of RB that mobilizes RB to deactivate E2 family (E2F) transcription factors, thereby driving cells into senescence. STING-IRF3-RB signaling plays a notable role in hepatic stellate cells (HSCs) within CCl4 or bile duct ligation (BDL)-induced murine models, pushing activated HSCs towards senescence. Accordingly, global IRF3 knockout or conditional deletion of IRF3 in HSCs aggravated liver fibrosis, a process mitigated by an FDA-approved CDK4/6 inhibitor. These findings underscore a straightforward yet vital mechanism of cGAS-STING signaling in inducing cellular senescence and unveil its unexpected biology in limiting liver fibrosis.