S-adenosyl-L-methionine-dependent protein-lysine N-methyltransferase that trimethylates 60S ribosomal protein L12 (rpl1201 and rpl1202) at 'Lys-4' and may dimethylate L12 also at 'Lys-40' and 'Lys-41'. Overexpression causes a severe growth defect. Has a role in meiosis. Belongs to the class V-like SAM-binding methyltransferase superfamily. RKM2 family.