PRMT1 and cancer: To further explore whether and how PRMT1-mediated cGAS methylation affects cGAS-dependent DNA sensing signaling in cancer cells, we established a HeLa cell line that stably over-expressed PRMT1 (Supplementary Fig. 1e) and found that PRMT1 overexpression robustly repressed cellular DNA sensing, reflected by reduced phosphorylation of STING and IRF3 after stimulation with DNA, including HT-DNA and ISD45 (Fig. 1f, Supplementary Fig. 1f, g).