Host RNA N6-methyladenosine and incoming DNA N6-methyldeoxyadenosine modifications cooperatively elevate the condensation potential of DNA to activate immune surveillance.

Self-non-self discrimination is fundamental to life, thereby even microbes can apply DNA modifications to recognize non-self DNA. However, mammalian cytosolic DNA sensors indiscriminately bind DNA, necessitating specific mechanism(s) for self-non-self discrimination. Here, we show that mammalian RNA N⁶-methyladenosine (m6A) and incoming DNA N⁶-methyldeoxyadenosine (6mdA) cooperatively elevate the condensation potential of DNA to activate immunosurveillance. RNA m6A modification was found to enhance the activation of cyclic guanosine monophosphate-AMP synthase (cGAS) via increasing DNA phase separation. And 6mdA further increased the phase separation potential of DNA. Consistently, host RNA m6A and incoming DNA 6mdA modifications cooperatively elevated the incoming DNA condensation and cGAS activation. Moreover, we developed a prodrug, QKY-613. QKY-613 promoted a discriminative incorporation of 6mdA into viral DNAs to elevate host immune surveillance, and decreased mortality in virus-infected aged mice. Our results link nucleic acid modification diversity with immune surveillance via phase separation, which might be targeted for therapeutic intervention.