FIGURE 9.

Arginine methylation of STAT1 was catalyzed by PRMT1. STAT1 methylation (immunoprecipitation (IP) with antibody to methyl- and dimethylarginine (MDA), Western blot with anti-STAT1 antibody) was detected by co-IP analysis. STAT1 protein was used as a loading control. STAT1 methylation levels were detected after HepG2.2.15 cells were transfected with siControl or siPRMT1. A, cells were treated with vehicle or IFN-α (1000 IU/ml) for 24 h. B and C, cells were pretreated with or without Dex (100 nm) or AdoMet (0.75 g/liter) for 16 h, followed by treatment with IFN-α (1000 IU/ml) for 8 h. The inset shows the ratio of STAT1-met/STAT1 with different treatments. *, p < 0.05; **, p < 0.01. Shown is a representative result from three independent experiments. IB, immunoblot; Nuc, nuclear protein; Cyto, cytoplasmic protein.