An EBV-inducible transcription factor complex (C1) binds to 4 different oligonucleotide probes derived from the

CD23a proximal promoter. Labeled oligonucleotides spanning potential transcription factor binding sites (probe A-D, Figure 1) were analyzed in EMSA by using nuclear extracts from B-CLL cell samples (Table 1), PBMCs from healthy donors (representative for n = 3), tonsillar B cells, Th cells, BL41 cells, and BL41/B95-8 cells as indicated. Major observed complexes (C1 in A-D, C2 in C,D) are indicated. The sequences of the different oligonucleotides used as probes are given in Figure 1.