Generation of clonal cell lines

KO cell lines were generated by limiting dilution, screened by Western blot, and verified by Sanger sequencing and functional assays. The STING/DNA-PK DKO U937 cell line was produced by transducing U937s simultaneously with a STING lentiCRISPR puro virus and a DNA-PK lentiCRISPR blasticidin virus, selecting in puro (10 μg/ml) and blasticidin (5 μg/ml), and seeding in 96-well plates immediately after selection. Very few colonies grew, and the verified DKO clone grew markedly slower than H1 control–targeted control clones or the STING KO clones, as expected (19).