Catalyzes the symmetrical dimethylation of arginine residues in targets such as small nuclear ribonucleoproteins, histone H2A/H4 and cbp-1 (PubMed:19521535, PubMed:21531333, PubMed:23866019, PubMed:22143770, PubMed:28158808). Dimethylation occurs in a distributive manner where the protein is released after the addition of the first methyl group prior to rebinding for the addition of the second methyl group (PubMed:23866019). Plays a role in the negative regulation of DNA damage-induced apoptosis (PubMed:19521535). By methylating cbp-1, may prevent apoptosis by repressing the capacity of cbp-1 to enhance cep-1 dependent transcription activation of the programmed cell death activator egl-1 (PubMed:19521535). Plays a role in heat and oxidative stress resistance (PubMed:28158808). L-arginyl-[protein] + 2 S-adenosyl-L-methionine = 2 H(+) + N(omega),N(omega)'-dimethyl-L-arginyl-[protein] + 2 S-adenosyl-L-homocysteine Optimum temperature is about 25 degrees Celsius. Homodimer (PubMed:22143770). Interacts with cep-1 (via C-terminus domain); does not methylate cep-1 (PubMed:19521535). Interacts with cbp-1 (via N-terminus domain and HAT domain); the interaction results in methylation of cbp-1 (PubMed:19521535). Component of a complex that contains cep-1 and cbp-1 (PubMed:19521535). May interact with pid-2, pid-4 and pid-5 (PubMed:33231880). Defective arginine methyltransferase activity with reduced symmetric dimethylation of targets (PubMed:28158808). Increased sensitivity to heat and oxidative stress (PubMed:28158808). Increased germ cell apoptosis following treatment with ionizing radiation (IR) or ethylnitrosourea and significantly enhanced IR-induced egl-1 levels (PubMed:19521535). Double knockout with prmt-1 results in prolonged larval development, shorter body size, reduced brood size, decreased egg-laying and 30% of eggs fail to hatch (PubMed:28158808). Double knockout also results in reduced asymmetric and symmetric arginine dimethylation of proteins (PubMed:28158808). Belongs to the class I-like SAM-binding methyltransferase superfamily. Protein arginine N-methyltransferase family.