Arginine methyltransferase that methylates the guanidino nitrogens of arginyl residues in proteins such as STAT3, FBL, histone H4 (PubMed:19405910). Acts as a coactivator (with NCOA2) of the androgen receptor (AR)-mediated transactivation (PubMed:17587566). Acts as a coactivator (with estrogen) of estrogen receptor (ER)-mediated transactivation (PubMed:12039952). Enhances PGR, PPARG, RARA-mediated transactivation (PubMed:12039952). May inhibit NF-kappa-B transcription and promote apoptosis (PubMed:16648481). Represses E2F1 transcriptional activity (in a RB1-dependent manner) (By similarity). May be involved in growth regulation (By similarity). Involved in C15ORF39-mediated inhibition of the microglial inflammatory responses through suppression of NF-kappa-B signaling, thereby reducing the production of pro- inflammatory cytokines (PubMed:38892217). {ECO:0000250|UniProtKB:Q9R144, ECO:0000269|PubMed:12039952, ECO:0000269|PubMed:16648481, ECO:0000269|PubMed:17587566, ECO:0000269|PubMed:19405910, ECO:0000269|PubMed:38892217}. This is the function of PRMT2 (protein arginine methyltransferase 2, ENSG00000160310).