Arginine methyltransferase that methylates (mono and asymmetric dimethylation) the guanidino nitrogens of arginyl residues present in target proteins. Constitutes the main enzyme that mediates monomethylation and asymmetric dimethylation of histone H4 'Arg-4' (H4R3me1 and H4R3me2a, respectively), a specific tag for epigenetic transcriptional activation (By similarity). Methylates ilf3 to regulate its DNA-binding activity (PubMed:18636753). Required for neural induction, playing a key role in the control of epidermal versus neural cell fate choice (PubMed:16214893). L-arginyl-[protein] + 2 S-adenosyl-L-methionine = 2 H(+) + N(omega),N(omega)-dimethyl-L-arginyl-[protein] + 2 S-adenosyl-L-homocysteine Homodimer. Homooctamer; individual homodimers associates to form a homooctamer and homooligomerization is required for proper localization to the cell membrane. Individual homodimers can associate to form a homohexamer (By similarity). Component of a complex with lsm14a/rap55a. Interacts with cirbp (By similarity). From the onset of gastrulation, expressed in dorsal mesoderm, and in dorsal and ventral ectoderm. At the neurula and tail bud stages, expression is restricted to the neuroectoderm, with highest expression in the anterior neural plate. Expressed both maternally and zygotically. Expressed throughout all embryonic stages. By Ca(2+). Belongs to the class I-like SAM-binding methyltransferase superfamily. Protein arginine N-methyltransferase family.