S-adenosyl-L-methionine-dependent methyltransferase that mediates N(3)-methylcytidine modification of residue 32 of the tRNA anticodon loop of tRNA(Ser), including tRNA(Ser)(UGA) and tRNA(Ser)(GCU) (PubMed:32923617, PubMed:34268557, PubMed:34862464, PubMed:34922197). Interaction with SARS1/SerRS is required for N(3)-methylcytidine methylation (PubMed:34268557).
