FIG. 3.

Spontaneous restoration of normal EBNA-3C expression in a 3B⁻/3C^low LCL after several months in culture. (A) Expression of the EBNA-3 proteins in a 3B⁻/3C^low LCL after prolonged culture. Whole-cell lysates were analyzed for expression of EBNA-3 proteins by Western blotting. EBV-immune serum was used to detect all the EBNA-3s, and the A10 monoclonal antibody was used to detect EBNA-3C alone. (B) Schematic of the mutation in the EBNA-3C restored 3B⁻/3C^low LCL. The DNA region between the EBNA-3A and EBNA-3C open reading frames was PCR amplified and sequenced. Kanamycin^R/Kan^R represents the kanamycin resistance cassette inserted in the place of the EBNA-3B ORF; FRT represents the FLP recombinase target sites flanking the Kan^r cassette; a and b represent nonviral, unique flanking sequences on either side of the FRT sites. The numbers of EBV nucleotides present between the nonviral insert and the EBNA-3A stop codon or EBNA-3C start codon are indicated by the numbered base pairs (bp).