FIG. 1.

Schematic of EBNA-3B mutations made in the EBV BAC. F plasmid sequences for prokaryotic replication were inserted into the EBV internal repeat 1 (IR1) region. The wild-type BAC contains the full complement of EBNA-3A, -3B, and -3C genes. EBNA-3B was knocked out in the 3B⁻/3C^low BAC by replacement of the entire EBNA-3B open reading frame with a kanamycin resistance cassette (Kan^r) flanked by FRT sites. The 3B⁻ BAC has been described previously and contains a single FRT site in place of the EBNA-3B open reading frame (2).