CGAS and viral infectious disease: Upon infection of DNA virus, the invaded cytosolic viral DNA is sensed by the cyclic GMP-AMP (cGAMP) synthase (cGAS).14,15 cGAS can also recognize mis-located cellular genomic DNA or mitochondrial DNA released into the cytosol upon mitostress triggered by viral infection or other stress conditions.16,17 Upon sensing of DNA, cGAS utilizes GTP and ATP as substrates to synthesize cGAMP, which binds to the ER-located adapter protein MITA (also called STING).18–20 This triggers the translocation of MITA from the ER via Golgi apparatus to perinuclear punctate structures.