Cells were plated on eight-well glass slides (EMD Millipore) and allowed to adhere for at least 24 h before use in experiments. As previously described (45 (link)), cells were fixed for 10 min with freshly prepared 4% (wt/vol) paraformaldehyde in PBS, permeabilized in 0.5% (vol/vol) Triton X-100 in PBS, blocked with MAXblock Blocking Medium (Active Motif), and incubated overnight with primary antibodies at 4 °C. After three washes in PBS, slides were incubated with fluorophore-conjugated secondary antibodies for 1 h at room temperature. Following an additional three washes in PBS, slides were mounted in ProLong Gold antifade reagent (Thermo Fisher Scientific) and imaged by confocal microscopy on a Leica SP8 instrument. Thirty cells from duplicated wells were selected randomly and detected the fluorescence intensity of Z-RNA (red channel) and A-RNA (green channel). Mean fluorescence intensity was quantified using Leica LAS X software. Primary antibodies were used for immunofluorescence studies: Z-RNA (clone Z22, Absolute Antibody; dilution: 1:200), A-RNA (clone 9D5; Millipore; dilution: 1:50).