Arginine methylation contributes to the regulatory roles of the DP C-tail. (A) Cartoon of DP arginine methylation (purple) and phosphosites (blue) identified. (B) DMSO-, MTA-, or AMI-1–treated SCC9s, assessed by immunofluorescence. (C) DMSO- or MTA-treated SCC9s, fixed at 0, 0.5, and 2.5 h in high calcium media, were assessed by immunofluorescence. (C′) Mean fluorescence intensity of DP at cell borders was calculated. *, P < 0.001. Error bars SEM. (D and D′) shCtr and shPRMT-1–treated SCC9s. PRMT expression was assessed by immunoblotting. Densitometry quantification of three independent experiments. *, P < 0.001. Error bars indicate SEM. (E) shCtr and shPRMT-1–transfected SCC9s stained with DP (NW6) and keratin antibodies, assessed by immunofluorescence. (F and F′) Phosphorylation (red arrow) of WT DP S-tag (DP CT) expressing cells transfected with shCtr or shPRMT-1 was assessed by immunoblotting. Densitometry quantification of three independent experiments. *, P < 0.001. Error bars indicate SEM. (G) S-tag pull-down confirms that PRMT-1 associates with WT DP S-tag (DP CT), assessed by immunoblotting. (H) SCC9s incubated with primary antibody pairs DP (1G4)-PRMT-1, DP-RIgG, or PRMT-1-MIgG antibodies, assessed by PLA. Nuclei stained with DAPI (blue). Bars, 10 µm. (H′) Quantification of PLA signal divided by number of nuclei performed from three independent experiments. *, P < 0.03. Error bars indicate SEM.