RB1 and neoplasm: PRMT5-catalyzed histone H3 arginine 8 (R8) and H4R3 symmetric dimethylation has been shown to repress expression of several tumor suppressor genes such as Suppressor of Tumorigenicity 7 (ST7), retinoblastoma (RB) family of tumor suppressors, and Protein Tyrosine Phosphatase Receptor-type O (PTPROt) [18, 21].