Arginine methyltransferase that can both catalyze the formation of omega-N monomethylarginine (MMA) and symmetrical dimethylarginine (sDMA), with a preference for the formation of MMA (PubMed:15485929, PubMed:19584108, PubMed:19858291, PubMed:21917714, PubMed:23133559, PubMed:28263986). Specifically mediates the symmetrical dimethylation of arginine residues in the small nuclear ribonucleoproteins Sm D1 (SNRPD1) and Sm D3 (SNRPD3); such methylation being required for the assembly and biogenesis of snRNP core particles. Methylates SUPT5H and may regulate its transcriptional elongation properties (By similarity). Mono- and dimethylates arginine residues of myelin basic protein (MBP) in vitro. May play a role in cytokine-activated transduction pathways. Negatively regulates cyclin E1 promoter activity and cellular proliferation (By similarity). Methylates histone H2A and H4 'Arg-3' during germ cell development (PubMed:16699504). Methylates histone H3 'Arg-8', which may repress transcription (PubMed:15485929). Methylates the Piwi proteins (PIWIL1, PIWIL2 and PIWIL4), methylation of Piwi proteins being required for the interaction with Tudor domain-containing proteins and subsequent localization to the meiotic nuage (PubMed:19584108). Methylates RPS10 (By similarity). Attenuates EGF signaling through the MAPK1/MAPK3 pathway acting at 2 levels. First, monomethylates EGFR; this enhances EGFR 'Tyr-1197' phosphorylation and PTPN6 recruitment, eventually leading to reduced SOS1 phosphorylation. Second, methylates RAF1 and probably BRAF, hence destabilizing these 2 signaling proteins and reducing their catalytic activity (PubMed:21917714). Required for induction of E-selectin and VCAM-1, on the endothelial cells surface at sites of inflammation. Methylates HOXA9. Methylates and regulates SRGAP2 which is involved in cell migration and differentiation (By similarity). Acts as a transcriptional corepressor in CRY1-mediated repression of the core circadian component PER1 by regulating the H4R3 dimethylation at the PER1 promoter (PubMed:23133559). Methylates GM130/GOLGA2, regulating Golgi ribbon formation. Methylates H4R3 in genes involved in glioblastomagenesis in a CHTOP- and/or TET1-dependent manner. Symmetrically methylates POLR2A, a modification that allows the recruitment to POLR2A of proteins including SMN1/SMN2 and SETX. This is required for resolving RNA-DNA hybrids created by RNA polymerase II, that form R-loop in transcription terminal regions, an important step in proper transcription termination. Along with LYAR, binds the promoter of gamma-globin HBG1/HBG2 and represses its expression. Symmetrically methylates NCL. Methylates p53/TP53; methylation might possibly affect p53/TP53 target gene specificity (By similarity). Involved in spliceosome maturation and mRNA splicing in prophase I spermatocytes through the catalysis of the symmetrical arginine dimethylation of SNRPB (small nuclear ribonucleoprotein-associated protein) and the interaction with tudor domain-containing protein TDRD6 (PubMed:28263986). L-arginyl-[protein] + 2 S-adenosyl-L-methionine = 2 H(+) + N(omega),N(omega)'-dimethyl-L-arginyl-[protein] + 2 S-adenosyl-L-homocysteine Activity is increased by EGF, HGF, FGF1 or FGF2 treatments, and slightly decreased by NGF treatment. Forms, at least, homodimers and homotetramers. Component of the methylosome complex, composed of PRMT5, WDR77 and CLNS1A. Found in a complex composed of PRMT5, WDR77 and RIOK1. RIOK1 and CLNS1A associate with PRMT5 in a mutually exclusive fashion, which allows the recruitment of distinct methylation substrates, such as nucleolin/NCL and Sm proteins, respectively (By similarity). Interacts with PRDM1 (PubMed:16699504). Identified in a complex composed of methylosome and PRMT1 and ERH. Interacts with EGFR; methylates EGFR and stimulates EGFR-mediated ERK activation. Interacts with HOXA9. Interacts with SRGAP2 (By similarity). Found in a complex with COPRS, RUNX1 and CBFB (PubMed:22193545). Interacts with CHTOP; the interaction symmetrically methylates CHTOP, but seems to require the presence of PRMT1 (PubMed:19858291, PubMed:22872859). Interacts with EPB41L3; this modulates methylation of target proteins. Component of a high molecular weight E2F-pocket protein complex, CERC (cyclin E1 repressor complex). Associates with SWI/SNF remodeling complexes containing SMARCA2 and SMARCA4. Interacts with JAK2, SSTR1, SUPT5H, BRAF and with active RAF1. Interacts with LSM11, PRMT7 and SNRPD3. Interacts with COPRS; promoting its recruitment on histone H4. Interacts with CLNS1A/pICln. Identified in a complex with CLNS1A/pICln and Sm proteins. Interacts with RPS10. Interacts with WDR77 (By similarity). Interacts with IWS1. Interacts with CRY1 (PubMed:23133559). Interacts with POLR2A. Interacts with SMN1/SMN2. Interacts with LYAR; this interaction is direct. Interacts with TTC5/STRAP; this interaction is DNA damage-dependent and promotes PRMT5 interaction with p53/TP53. Interacts with p53/TP53 in response to DNA damage; the interaction is TTC5/STRAP dependent. Interacts with FAM47E; the interaction is direct, promotes PRMT5 localization to chromatin, and does not disrupt its association with WDR77 or STUB1 (By similarity). Interacts with TDRD6 (PubMed:28263986). Interacts with STUB1 (By similarity). Belongs to the class I-like SAM-binding methyltransferase superfamily. Protein arginine N-methyltransferase family.