Identification of p33. (A) Reactivity of H8 monoclonal antibody. Protein extracts from BL21(DE3)Lys transformed with pGEX2T, pET30a, pGEX2T-ORF69 (ORF69-GST), or pET30a-ORF69(ORF69-His) were analyzed by Western blotting after IPTG induction. (B) Expression of ORF69-encoded protein in different PEL cell lines analyzed by Western blotting. The H8 monoclonal antibody revealed a 33-kDa-specific band (p33) after KSHV lytic cycle induction with TPA in BCBL-1, BC3, and BC1. B95-8 cells were treated with TPA and butyrate. Anti-BFLF2 antibody showed EBV activation. Anti-β-actin was used to calibrate the protein loading.