FIG 3.

BHLF1 protein expression is enhanced by SM. EBV-negative Louckes BL cells were cotransfected with an expression vector encoding FLAG-tagged BHLF1 (origin, B95.8 EBV DNA) and 5 or 10 μg of the expression vector for the EBV SM protein or the empty pcDNA3 expression vector. +, −, and the closed triangle indicate the presence, absence, and increasing amounts of the indicated expression vector, respectively. All transfection mixtures contained an equal amount of plasmid DNA, adjusted with the empty expression vector (20 μg total plasmid DNA [lanes 1 to 3] and 10 μg total plasmid DNA [lanes 4 and 5]). Protein expression was detected by immunoblotting for the FLAG epitope (BHLF1 and insulin-degrading enzyme [IDE], a positive control for the detection of FLAG) or α-actin (gel-loading control). Results are representative of data from four experiments, each of which revealed a dependence on SM for efficient BHLF1 protein expression.