293T, A549, HeLa, HeLa-S3, WT-MEF, MEFSting−/−, MEFcGas−/−, MEFTrex1−/−, T98G, and T98GF/H-cGAS were maintained in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS), 1% penicillin/streptomycin, and 1% glutamine. T98G overexpressing F/HA-cGAS were generated by transducing parental T98G with viral particles produced by using the pOZ-F/HAcGAS construct and selected with puromycin. Cells were maintained in DMEM supplemented with 10% FBS, 1% penicillin/streptomycin, and 1% glutamine. A549 were obtained from S. Goodborn. WT-MEF, MEFSting−/−, and MEFcGas−/− were a gift of S. R. Paludan, MEFTrex1−/− were obtained from J. Rehwinkel, and parental T98G were obtained from C. Goujon.