S-adenosyl-L-methionine-dependent methyltransferase that mediates N(3)-methylcytidine modification of residue 32 of the tRNA anticodon loop of tRNA(Thr) and tRNA(Ser). N(3)-methylcytidine methylation of tRNA(Thr) requires the N6-threonylcarbamoylation of tRNA (t6A37) by the EKC/KEOPS complex as prerequisite. N(3)-methylcytidine methylation of tRNA(Ser) requires the formation of N(6)-dimethylallyladenosine(37) (i6A37) by MOD5 as prerequisite. Methylation of tRNA(Ser) is also stimulated by SES1. Binds F-actin and shows weak F-actin cross-linking activity