The pattern recognition receptors cGAS and IFI16 do not bind and initiate STING-dependent IFN-I signaling on dsDNA fragments containing deoxy-uracil 4473

Description DNA damage and cytoplasmic DNA fragments induce type-1 interferons (IFN-1) and enhance responses to immune checkpoint inhibitors. Our previous work showed that ATR inhibitors (ATRi), which target DNA damage response kinases, induce IFN-1 and promote deoxyuridine (dU) incorporation by DNA polymerases, similar to antimetabolites. However, the impact of dU-containing DNA on IFN-1 signaling remains unclear. In this study, we demonstrate that uracil DNA glycosylase (UNG) plays a crucial role in ATRi-induced IFN-1 responses. While ATRi induces a similar number of micronuclei in both UNG wild-type and knockout cells, cytoplasmic DNA fragments and dU-containing micronuclei are increased in UNG knockout cells. Surprisingly, synthetic DNA fragments containing dU inhibit STING-dependent IFN-1 and MHC-I induction. Moreover, we found that neither cGAS nor IFI16 binds to dU-containing DNA fragments. These findings reveal that dU-containing DNA suppresses cGAS- and IFI16-dependent, STING-dependent IFN-1 responses.