Non-canonical immune response to the inhibition of DNA methylation via stabilization of endogenous retrovirus dsRNAs

5-Aza-2'-deoxycytidine, also known as decitabine, is a DNA-methyltransferase inhibitor (DNMTi) used to treat acute myeloid leukemia (AML). Decitabine activates the transcription of endogenous retroviruses (ERV), which can induce an immune response by acting as cellular double-stranded RNAs (dsRNAs). Here, we employ an image-based screening platform to identify dsRNA-binding factors that mediate the downstream effect of ERV induction. We find that Staufen1 (Stau1) knockdown decreases the interferon signature and rescues decitabine-mediated cell death. Moreover, Stau1 directly binds to ERV RNAs and stabilizes them, together with a long non-coding RNA TINCR. We further show that TINCR enhances the interaction between Stau1 and ERV RNAs. Analysis of a clinical patient cohort reveals that AML patients with low Stau1 and TINCR expressions exhibits inferior treatment outcomes to the DNMTi therapy. Our study reveals that decitabine-mediated cell death is a consequence of complex interactions among different dsRNA-binding proteins for access to their common dsRNA targets. HIGHLIHGTSO_LIImage-based RNAi screening reveals multiple dsRBPs regulate response to decitabine C_LIO_LIStau1 binds to ERV RNAs and affects their stability and subcellular localization C_LIO_LITINCR binds to Stau1 and enhances Stau1-ERV interactions C_LIO_LIAML/MDS patients with low Stau1 and TINCR expressions show poor response to DNMTis C_LI