NF-κB is constitutively activated in KSHV-infected PEL cell lines and patient specimens.

(A), Nuclear proteins extracted from latent cultures of BC1, BC2, and BC3 cells were examined by EMSA for DNA binding using a radiolabeled NF-κB–specific probe. All 3 PEL cell lines demonstrated protein/DNA binding with 2 distinct complex formations, compared with the uninfected negative control cell line BJAB. Cold competition using 50-fold molar excess of unlabeled NF-κB and Oct-1 oligonucleotides demonstrated the specificity of the protein/DNA binding complexes. (B), NF-κB activity in ex vivo KSHV-infected PEL cells was assessed by EMSA. Mononuclear cells were purified from 2 different patient effusions specimens, and the nuclear proteins were extracted and assessed for NF-κB/DNA binding. In one case, the amount of binding in the ex vivo specimen surpassed that of the BC5 cell line subsequently established from the same specimen. BJAB was used as the negative control for NF-κB activity.