PRMT5 is overexpressed in EBV⁺ primary lymphomas, EBV-transformed and EBV-immortalized B cells. (A) Immunohistochemical nuclear/cytoplasmic expression of both PRMT5 and its epigenetic marks, S2Me-H3R8 and S2Me-H4R3, in Burkitt lymphoma (BL) (left column: ×400) and plasmablastic lymphoma (PL) (second column, from left; ×400); examples of nuclear dark red positivity are highlighted by black arrows and in the insets. The pattern of PRMT5, S2Me-H3R8, and S2Me-H4R3 expression in germinal centers (GCs) and mantle zone (MZ) of reactive lymph nodes is illustrated (third column, from left: ×400). Images of negative controls are shown (×400). (B) Western blot of PRMT5 expression in resting (RB), activated B cells (AB), and transformed LCLs obtained from hu-PBL-SCID mouse lymphomas generated from 4 separate donors (60A, C7M3, 100, 147). (C) Western blot of PRMT5 expression in RB, AB cells, and fully immortalized LCLs generated by infecting with EBV normal B cells from 6 separate healthy donors (C7M3, D-9, D-22, D-27, D-28, D-32). (D) Western blot of PRMT5 expression at various time points following in vitro infection of normal B cells with EBV. LCL is a fully immortalized cell line; Jurkat was used as positive control. Actin used as loading control. (E-G) Confocal microscopy of PRMT5 (E), LMP1 and EBNA2 (F), and PRMT5 epigenetic marks, S2Me-H4R3 and S2Me-H3R8 (G), at various time points following in vitro EBV infection of normal B cells. LCL is a fully immortalized cell line (G); C7M3 is a fully transformed cell line used as positive control (E).