FIG. 3.

Encapsidation of the BPV1 genome by L1 and L2 deletion mutants in BPHE-1 cells. BPHE-1 cells, which harbor 50 to 200 BPV1 episomes per cell, were coinfected with recombinant SFV expressing BPV1 L1 and L2 deletion mutants, and 30 h postinfection, the cells were harvested and lysed. By using rabbit anti-BPV1 L1 VLP, L1 was immunoprecipitated from lysates containing L1 (lanes 2 and 4 to 8) and full-length L2 (lanes 3 and 4), full-length HPV16 L2 (lane 5), L2Δ2–9 (lane 6), L2Δ461–469 (lane 7), and L2Δ422–431 (lane 8) or from crude extract of bovine wart (lane 9). The immunoprecipitates were treated with DNase I for 1 h and washed. Undigested DNA present in the immunoprecipitates was recovered and separated on a 0.8% agarose gel with a biotinylated HindIII digest of λ (lane 1). The presence of viral DNA was detected by Southern blotting with a biotinylated probe corresponding to the EcoRI-BamHI large fragment of the BPV1 genome.