Known as: S-adenosyl-L-methionine:histone-arginine omega-N-methyltransferase activity, nuclear protein (histone) N-methyltransferase activity, histone protein methylase activity
Catalysis of the reaction: S-adenosyl-L-methionine + (histone)-arginine = S-adenosyl-L-homocysteine + (histone)-N-methyl-arginine. [EC:2.1.1.125]